1. Field of the Invention
The present invention relates to converting colors using a color look-up table in order to create colors to be displayed/output on/to an appropriate display or output unit, and more particularly to a method for generating the color look-up table and converting colors using the same.
2. Description of the Related Art
Various devices reproducing colors, such as scanners, printers, monitors, and mobile LCDs, have been made more multi-functional, more high-quality, and more inexpensive in order to satisfy users' various needs. The color reproduction devices have used different color spaces or color models according to application fields. For example, a Red-Green-Blue (RGB) color space has been used in a computer monitor field, and a Cyan-Magenta-Yellow-Black (CMYK) color space has been used in a printing field. Further, a Commission International de I'Eclairage (CIE) color space has been used to define a device-independent color, which can exactly reproduce colors in any device. The CIE color space may be classified into CIE-XYZ, CIE L*a*b*, and CIE LUV color spaces. Being easily used and expressing a great amount of colors, the CIE color space is widely used in computers.
The RGB color model is mainly used to express the colors in digital images. However, the RBG color model is not apparatus-independent and renders accurate color correction difficult. Thus, a color conversion operation is generally carried out in order to convert the RGB color model into the CIE L*a*b color model, etc.
Conventional color conversion technologies have used an approximation method in the simple form of interpolation based on a color look-up table or multi-nominal regression equation. There is a need in the art to reduce storage space and to improve conversion performance. Referring to FIG. 1, the interpolation based on the color look-up table, which is the best popular color conversion technology, can be carried out as follows. First, during the conversion of the entire color space, some of colors are sampled and stored in the form of a color look-up table. The residual colors that are not stored in the color look-up table, are converted using various interpolation methods such as tetrahedral interpolation and trilinear interpolation, etc.
Pairs of color values before and after the conversion of colors are stored in the color look-up table. In FIG. 1, RGB item indicates the colors before the conversion of the colors, and Lab item shows the colors after the conversion of the colors. In the case where the color format can be predicted before the conversion, it is possible to store only the converted colors in the color look-up table. If the colors in the color look-up table are sequentially defined at intervals of 51, for example, [0, 0, 0], [0, 0, 51], [0, 0, 102], . . . , [204, 255, 255], and [255, 255, 255], the colors cannot be stored in the color look-up table efficiently.
Such an interpolation method based on the color look-up table has high accuracy and high speed operation, as compared with the method using the multi-nominal regression equation. Disadvantageously, however, the interpolation method requires a large space to store its color values.